<!DOCTYPE html>
<html>
<head>
    <title>Sealed Objects Example</title>
</head>
<body>
    <p>This only works in browsers that natively support ECMAScript 5.</p>
    <script>
        var person = { name: "Nicholas" };
        Object.seal(person);
        
        person.age = 29;
        alert(person.age);      //undefined
        
        delete person.name;
        alert(person.name);     //"Nicholas"
    </script>
</body>
</html>
